1. Field of the Invention
This invention relates to an optical disc and its information recording method and apparatus.
2. Description of the Related Art
In a recording type optical disc, preformat information is recorded in advance on the optical disc. When an information recording apparatus for optical discs records data on the optical disc, it detects the preformat information, refers to this detected information, and decides a recording position of the data.
The optical disc has a spirally formed recording track. The recording track is divided into Physical segments having a predetermined length, and an address is assigned to each segment. This address is written as the preformat information into each segment.
In a method for writing the preformat information, recording is achieved by prepits on the track. Recently, there has been a method for recording the preformat information by forming a groove and a land on a surface of the optical disc, forming a meandering wobble signal on the side walls of the groove, and modulating this wobble signal.
On the other hand, as to data to be recorded as user data on the recording track, codes for error correction are usually added to original data, which is divided into smaller synchronous frames to become data to be recorded. For example, in a DVD (digital versatile disc), an error correction code block (ECC blocks) is modulated, synchronous codes are added at predetermined intervals, a plurality of synchronous frames is generated, and rows of the plurality of synchronous frames result in the data to be recorded. It should be noted that the user data here means such data that is recorded on the optical disc and reproduced by a user using a recording/reproduction apparatus, unlike the preformat information.
There are the following documents concerning the optical disc.
Jpn. Pat. No. 2,663,817, according to this document, (document 1) . . . identification information is shared by the land (L) and groove (G) and deviates from a center of the land and groove. This is associated with a current DVD-RAM disc standard.
Jpn. Pat. Appln. KOKAI Publication No. 04-172623, Jpn. Pat. Appln. KOKAI Publication No. 2000-11460, according to these documents, a recording mark is formed at a groove position, and a land portion has land prepits for addresses. This is associated with current DVD-RW discs and DVD-R discs.
Jpn. Pat. Appln. KOKAI Publications No. 11-149644, and No. 2001-34952, according to these documents, a method for recording in the land (L)/groove (G) is shown, wherein address information is recorded by wobble modulation using Gray codes.
Greater capacity has recently been desired in the optical discs. In order to accomplish this, so called land-groove optical discs have been developed which use both the groove formed on an optical disc substrate and the land between the grooves as the recording track. Further, concerning the preformat information, research is being conducted into methods for recording the wobble signal after modulating. The reason is that data recording areas can be efficiently utilized as compared with the method in which the prepits are recorded. In other words, when the method in which the prepits are recorded is adopted, recording of the user data is physically restricted in parts where the prepits are formed.
Here, when adopting the method in which the wobble signal is modulated to record the preformat information, the inventor has focused attention on an important relationship between a position of the preformat information, and a recording start position and a recording end position of the user data. In other words, so-called additional recording is performed in a rewritable optical disc wherein the user data is recorded by being tied to an already-recorded portion. Further, overwrite recording may sometimes be performed on a portion where the recorded user data has already been recorded. The overwrite recording may sometimes be executed repeatedly in the same area. In such a case, if the position of the preformat information and the recording start position of the user data exit in the same area, such problems occur as that the preformat information is deformed and a detection level is lowered.